A141427 a(n) = phi(A067775(n)).

1, 4, 10, 16, 22, 28, 30, 40, 46, 52, 58, 60, 70, 72, 82, 88, 100, 106, 112, 130, 136, 138, 148, 150, 156, 166, 172, 178, 180, 190, 196, 198, 210, 226, 232, 238, 240, 250, 256, 262, 268, 270, 280, 282, 292, 310, 316, 330, 336, 346, 352, 358, 366, 372, 382, 388

Offset

1,2

Comments

Count of numbers smaller than and coprime to p for primes p such that p + 4 is composite.

Subsequence of A006093.

Links

Table of n, a(n) for n=1..56.

Prog

(PARI) {forprime(p=2, 400, if(!isprime(p+4), print1(eulerphi(p), ", ")))} \\ Klaus Brockhaus, Aug 31 2008

Crossrefs

Cf. A067775, A000010 (Euler totient function), A006093 (primes minus 1), A141426, A141515.

Sequence in context: A310524 A140493 A219239 * A310525 A310526 A310527

Adjacent sequences: A141424 A141425 A141426 * A141428 A141429 A141430

Keyword

nonn

Author

Giovanni Teofilatto, Aug 06 2008

Extensions

More terms from Robert G. Wilson v, Aug 18 2008

Edited by N. J. A. Sloane and Klaus Brockhaus, Aug 31 2008

Status

approved